Chapter 15 Frequencies and Distributions

Question 1

Distribution

Answer 1

Shape and spread of data sets/populations

Question 2

Frequency

Answer 2

How often a certain event (e.g. score) occurs

Question 3

Frequency Distribution

Answer 3

Distribution showing how often certain values occur

Question 4

Percentile

Answer 4

Point on a measured scale that marks of certain percentages of cases in an ordered data set

Question 5

Deciles

Answer 5

Points on a measured scale that mark off each 10% of the data set or population

Question 6

Quartiles

Answer 6

Points on a measured scale that mark the 25th, 50th and 75th percentiles of a distribution

Question 7

Normal Distribution

Answer 7

Continuous distribution, bell-shaped, symmetrical about its mid-point

Question 8

z score/value

Answer 8

Alternative term for standard score

Question 9

Standard Score

Answer 9

Number of standard deviations a particular score is from its sample mean

Question 10

Sampling Error

Answer 10

Difference between a sample statistic and the true population statistic, usually assumed to be random in origin

Question 11

Sampling Distribution (of Means)

Answer 11

Theoretical distribution that would be obtained by taking the same statistic from many same size randomly selected samples (e.g. the mean)

Question 12

Standard Error

Answer 12

Standard deviation of a sampling distribution

Question 13

Central Limit Theorem

Answer 13

Used in the theoretical estimation of the standard error of a sampling distribution from the standard deviation of a sample

Question 14

Confidence Intervals/Limits

Answer 14

Estimated limits (e.g. with 95% confidence) to the likely range (interval) within which a population mean lies, based on an estimate from a sample mean and standard error

Question 15

Skew/Skewed Distributions

Answer 15

Non-normal distributions that have a lot more extreme scores on one side of the mode than on the other

Question 16

Ceiling Effect

Answer 16

Occurs where measure produces most values near the top of a scale - e.g. easy test

Question 17

Positively Skewed Distribution

Answer 17

Description of distribution that contains a longer tail of higher values

Question 18

Floor Effect

Answer 18

Phenomenon where measure produces very many low scores - e.g. difficult test

Question 19

Kurtosis

Answer 19

Overall shape of a distribution in terms of height and with compared with normal distribution

Question 20

Platykurtic Distribution

Answer 20

Non-normal distribution that is widely spaced out and low in the centre

Question 21

Leptokurtic Distribution

Answer 21

Non-normal distribution that is closely bunched in the centre and tail